Many of switching regulators, charge pumps, driver ICs and the like conventionally have, as an output stage, a pair of switch devices that are connected in series between two different potentials.
In driving such pair of switch devices, it is important to prevent them from being simultaneously turned on in order to prevent a flow-through current from destroying devices and reducing efficiency.
FIG. 6 is a circuit block diagram showing a conventional example of a switch driver circuit.
As shown in FIG. 6, the switch driver circuit of this conventional example includes: switch devices N1 and N2; comparators CMP1 and CMP2 for monitoring a gate signal “a1” of the switch device N1 and a gate signal “a2” of the switch device N2, respectively; an AND operator AND1 for performing an AND operation between a monitor signal “b1” of the comparator CMP1 and a drive signal CLK; and an AND operator AND2 for performing an AND operation between a monitor signal “b2” of the comparator CMP2 and the drive signal CLK, and generates a simultaneous OFF-period “d” of the switch devices (see FIG. 7), during which both of them are turned off, by controlling the gate signal of each one of the pair of switch devices according to a monitor result of monitoring the gate signal of the other one of the pair of switch devices.
More specifically, the gate signal “a1” is shifted from low level (L) to high level (H) when both the drive signal CLK and the monitor signal “b2” are high level (H). That is, the switch device N1 is turned on after the switch device N2 is turned off. On the other hand, the gate signal “a2” is shifted from low level (L) to high level (H) when the drive signal CLK is low level (L) and the monitor signal “b1” is high level (H). That is, the switch device N2 is turned on after the switch device N1 is turned off.
As an example of the conventional technology related to the above description, Patent Document 1 listed below discloses and proposes a switching power supply comprising: first and second transistors; driving means for alternately allowing the first and second transistors to conduct; a transformer whose primary winding forms part of current paths through the first and second transistors, wherein the driving means is formed of: means for generating a rectangular waveform signal; detecting means for detecting that a current flowing through one of the first and second transistors is flowing through the primary winding, and for generating a detection signal while the current is being detected; and means for alternately generating, by combining the rectangular waveform signal and the detection signal, first and second drive signals that are shorter than a half cycle of the rectangular waveform signal by storage times of the first and second transistors, respectively, and the first and second drive signals are base drive signals of the first and second transistors, respectively.
Also, many electronic circuits such as a switching regulator, a charge pump, and a driver IC conventionally incorporate a timer latch type protection circuit as protection means that performs a predetermined protection operation when a circuit abnormality is detected.
As an example of the technology related to the above description, Patent Documents 2 and 3 listed below each disclose and propose a switching power supply circuit that achieves a load short-circuit protection function by using a timer latch type protection circuit that monitors an output voltage.
Also, conventionally, electronic circuits such as a switching regulator, a charge pump, and a driver IC are often provided with an overcurrent protection function of performing a predetermined protection operation when generation of an overcurrent is detected.
As an example of the technology related to the above description, Patent Document 4 listed below discloses and proposes an overcurrent protection circuit of a self-oscillation type direct current-direct current converter that exploits blocking oscillation, wherein the overcurrent protection circuit is provided with: an output voltage reduction detection circuit for detecting reduction of an output voltage when an abnormality such as an overload and a short circuit has occurred and stopping oscillation of a switching device when the output voltage is at a predetermined level or lower; and a start-up detection operation stopping circuit for stopping operation of the output voltage reduction detection circuit only at a start-up time when power is turned on.
Also, oscillation circuits that generate a signal such as a triangular waveform signal and a pulse signal have conventionally been used in various electronic circuits such as a switching regulator, a charge pump, and a driver IC.
In particular, for the purpose of giving the user a higher degree of freedom in setting, many electronic circuits provided with an oscillation circuit are configured such that the oscillation frequency can be adjusted as necessary via an external device (such as a resistor and a capacitor) (see, for example, Patent Document 5 listed below).    Patent Document 1: JP-A-S59-113774    Patent Document 2: JP-A-S63-274363    Patent Document 3: JP-A-H10-136644    Patent Document 4: JP-A-H06-38520    Patent Document 5: JP-A-H04-334114